VORTEX FORMATION ON JOSEPHSON-JUNCTION LATTICES

Using relaxation techniques, the authors have simulated the flow of cu rrent vortices caused by a magnetic field applied perpendicular to a t wo dimensional lattice whose sites are connected by Josephson junction s. The inception of vortex flow coincides in each case with a reductio n in the energy of the lattice. Different boundary conditions give ris e to a different initial number of vortices, but energies per junction remain approximately the same regardless of the boundary conditions. In each case, the threshold magnetic field decreases inversely with th e number of junctions in the lattice. A square ''honeycomb'' lattice, i.e. with each Josephson junction connected to nearest three instead o f four neighbors, displays the similar behavior in an applied external magnetic field as an ordinary square lattice.